1. Field of the Invention
The present invention relates to a device for braking the movable press plate and the plunger in a hydraulic press employed particularly for the mold-pressing of fiber reinforced synthetic materials. The press plate is guided laterally and includes spindles (abutment members) attached thereto which act on and are braked by at least two countersupport cylinder units mounted on the stationary press table or the press stand.
2. Description of the Prior Art
In hydraulic presses used for processing fiber reinforced plastics, it is necessary that the two tool halves move with a high-precision alignment relative to one another during the pressing process. Such precise movement cannot be realized with the prior art mechanical guides.
Presses have therefore been developed in which, after the driven plunger moves the press plate with a rapid closing speed, countersupport cylinder units brake the plunger and the press plate while simultaneously aligning the final pressing movement of the press plate. When mold-pressing fiber reinforced plastics, such presses encounter a problem in that the highly reactive resin mats to be processed permit only a very short period of time for the material to dwell without pressure in the heated lower tool portion. Therefore, the time from insertion of the material to closing of the press must be kept as short as possible. Consequently, extremely high speeds have been employed for closing the press, e.g. up to 1 m/s. In practice this speed cannot be increased any further because it would incur excessive additional costs. Further, before the press plate is connected with the countersupport cylinder units, the velocity of the press plate must be reduced to almost zero so as to permit a force-transmitting and/or form-locking connection between the spindles mounted on the press plate and the countersupport units mounted on the press stand. This occurrence, however, may involve such a delay that the advantages of a rapid closing are lost.